High pressure swivel joint

ABSTRACT

A high pressure swivel joint used in pipe assemblies transferring high pressure fluid. The swivel joint comprises a first pipe section and a sleeve-like second pipe section. The first pipe section is inserted into the second pipe section and the sections are relatively rotatable. A wear ring is positioned within a recess formed in the inner wall of the first pipe section. A second wear ring is positioned within a recess formed in the inner wall of the second pipe section.

SUMMARY

The invention is directed to a swivel joint comprising a tubular firstmember and a tubular second member. The tubular first member has a firstlongitudinal axis, a connection end, and an external face formed at theconnection end of the first member. The tubular second member has afirst longitudinal axis, a connection end, and a recessed internal facewithin the connection end and extending normal to the first longitudinalaxis. The connection end of the first member is coaxially receivedwithin the connection end of the second member. The first and secondmembers are relatively rotatable. A first wear ring is positionedadjacent an inner wall of the connection end of the first member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a swivel joint of the presentinvention.

FIG. 2 is a perspective view of the swivel joint shown in FIG. 1.Portions of the second pipe section and seal have been cut away forbetter display.

FIG. 3 is the perspective view of the swivel joint shown in FIG. 2.Portions of the first and second pipe sections have been cut away forbetter display. The seal within the swivel joint is shown intact.

FIG. 4 is a cross-sectional view of the second pipe section shown inFIG. 3. The first pipe section and the seals are removed to better showthe inner portions of the second pipe section.

FIG. 5 is a cross-sectional view of another embodiment of the swiveljoint, similar to that shown in FIG. 1, but with a second seal added.

FIG. 6 is a cross-sectional view of an alternative embodiment of theswivel joint of the present invention.

FIG. 7 is a perspective view of the swivel joint shown in FIG. 6.Portions of the second pipe section and seal have been cut away forbetter display.

FIG. 8 is the perspective view of the swivel joint shown in FIG. 7.Portions of the first and second pipe sections have been cut away forbetter display. The seal within the swivel joint is shown intact.

FIG. 9 is a cross-sectional view of another embodiment of the swiveljoint, similar to that shown in FIG. 6, but with a second seal added.

FIG. 10 is a cross-sectional view of another embodiment of the swiveljoint of the present invention. A portion of the swivel joint is shownenlarged for better display.

FIG. 11 is a cross-sectional view of another embodiment of the swiveljoint, similar to that shown in FIG. 10, but a gasket has been addedbetween the pipe sections. A portion of the swivel joint is shownenlarged for better display.

FIG. 12 is a cross-sectional view of another embodiment of the swiveljoint of the present invention.

FIG. 13 is a cross-sectional view of another embodiment of the swiveljoint of the present invention.

FIG. 14 is a top plan view of a wear ring for use with the swivel jointsshown in FIGS. 12 and 13.

FIG. 15 is a side elevation view of the wear ring of FIG. 14.

FIG. 16 is a perspective view of the wear ring of FIG. 14.

DETAILED DESCRIPTION

Swivel joints are connections between pipe sections that containbearings. The bearings allow the pipe sections to rotate about oneanother so that the pipe sections may be oriented in differentdirections. High pressure swivel joints are typically used with pipeassemblies that transfer fluid at high pressure and flow rates, such as5,000 to 22,500 psi. A high pressure swivel joint, for example, may beused with pipe assemblies used in oil and gas hydraulic fracturingoperations. It is important that high pressure swivel joints containadequate seals to prevent fluid from leaking from the joint.

With reference to FIGS. 1-3, a high pressure swivel joint in is shown.The joint 10 comprises a tubular first member or pipe section 12 and atubular second member or pipe section 14. The pipe sections 12, 14 arepreferably made out of metal. However, the pipe sections 12, 14 may bemade out of other materials capable of withstanding high amounts offluid pressure. A passage 16 is formed within each pipe section 12, 14.Fluid flows between the pipe sections 12, 14 through the passage 16.

Referring now to both FIGS. 1 and 2, the first pipe section 12 has afirst end or connection end 18. The first end 18 is attached to orintegral with an arcuate body section 20. A portion of the body 20 isshown in FIG. 1. The body 20 may connect to another pipe section at itsopposite second end (not shown). The first end 18 has an external faceor first surface 22. The first surface 22 is perpendicular to thelongitudinal axis of the first end 18 and has an opening 24, as shown inFIG. 2. The opening 24 opens into the passage 16.

The second pipe section 14 has a connection end or sleeve 26. The sleeve26 is attached to or integral with a linear body section 28.Alternatively, the body 28 may be arcuate in shape. The body 28 connectsto another pipe section (not shown).

The sleeve 26 has a recessed internal face or internal surface 30 thatis perpendicular to the longitudinal axis of the sleeve 26 and has anopening 32, as shown in FIG. 4. The opening 32 opens into the passage16. The sleeve 26 has a circular sleeve opening 34 formed at its firstend 36. The diameter of the sleeve opening 34 is larger than the outsidediameter of the first end 18 of the first pipe section 12. The first end18 of the first pipe section 12 is coaxially received or disposed withinthe sleeve 26 through the sleeve opening 34. When the pipe sections 12,14 are connected, the body 20 of the first pipe section 12 is in closeproximity to the first end 36 of the sleeve 26.

Continuing with FIGS. 1-3, the joint 10 does not have a seal between thefirst surface 22 of the first end 18 and the internal surface 30 of thesleeve 26. Instead, the first surface 22 and the internal surface 30 arecoaxial and in contact with one another. A seal or buffer may be placedbetween the surfaces 22, 30 to serve as a cushion.

Fluid is prevented from entering the joint 10 by a first radial seal 38.The seal 38 is annular and surrounds the outer circumference of thefirst end 18. The seal 38 is concentric with the first end 18 of thefirst pipe section 12, as shown in FIG. 3. The seal 38 is a rotary seal,meaning the seal 38 allows for rotation of the first end 18 within thesleeve 26. An example rotary seal is a u-cup seal. A u-cup seal may havea rectangular profile and contain a cup section and an annular lip. Theseal 38 may also have a circular profile, like an O-ring.

The seal 38 may be made from any type of elastic material capable ofsealing fluid. For example, the seal 38 may be made from nitrile,polyresin, silicone, or is polyurethane. The seal 38 is preferablyconfigured to withstand fluid pressure up to at least 22,500 psi.

The first seal 38 fits within a first annular groove 40. The groove 40is formed around the outer surface of the first end 18 of the first pipesection 12. The groove 40 is axially spaced from the first surface 22 ofthe first end 18, and is characterized by a pair of parallel side walls42 joined by a base 44, as shown in FIG. 3. When the seal 38 is insertedinto the groove 40, the seal 38 will contact both side walls 42 and thebase 44 of the groove 40. The seal 38 seals against the innercircumference of the sleeve 26, as shown in FIG. 1. The seal 38 does notcontact either of the surfaces 22, 30. The seal 38 only contacts thegroove 40 and the inner circumference of the sleeve 26.

The seal 38 may also be positioned around the first end 18 and axiallyspaced from the first surface 22, but not positioned within a groove. Insuch embodiment, the first end 18 would not contain the groove 40.Instead, the seal 38 would be radially compressed between the first end18 and the sleeve 26.

During operation, high pressure fluid passing through the joint 10 maycause the pipe sections 12, 14 to pulsate, which may cause damage to thesurfaces 22, 30 or surrounding areas of the pipe sections. For example,the surfaces 22, 30 may chip or warp. Over time, the high pressure fluidmay also corrode or erode the surfaces 22, 30 or surrounding areas ofthe pipe sections 12, 14. If the surfaces 22, 30 or surrounding areasare damaged or eroded, fluid may leak during operation from between thesurfaces 22, 30.

The seal 38 is not affected by damage to or erosion of the surfaces 22,30, because the seal 38 is not positioned between the surfaces 22 and30. Rather, the seal 38 is axially spaced from the surfaces 22, 30 andfunctions as a radial seal. Any fluid that leaks from between thesurfaces 22, 30 will be stopped by the seal 38. In contrast, damage toor erosion of the surfaces 22, 30 might prevent a facial or packing sealpositioned between the surfaces 22, 30 from sealing properly. Propersealing is prevented because some of the sealing surface of the surfaces22, 30 has been lost, resulting in gaps for fluid to pass through.

The surfaces 22, 30 may also need to be polished or ground during itslifetime to keep the joint 10 operating properly. This is considered therebuilding or reworking of the joint 10, The rebuild or rework of thejoint 10 may decrease the surface area of the surfaces 22, 30, furtherdecreasing the compression of the surfaces 22, 30 upon each other duringoperation. If a packing seal is used, the surfaces 22, 30 may no longerseal properly against the packing seal if the joint 10 has been rebuilt.However, the seal 38 is not affected by the rework process because theseal is spaced axially from the surfaces 22, 30 of the pipe sections 12,14.

The seal 38 is also not affected by the pulsations of the pipe sections12, 14, because it is not repeatedly compressed by the surfaces 22, 30as the pipe sections 12, 14 pulsate. In contrast, the pulsation of thepipe sections 22, 30 will continually compress a packing seal usedbetween the surfaces 22, 30, which may cause damage to the packing sealand prevent it from sealing properly. High pressure fluid flowingthrough the joint 10 may also cause the pipe sections 12, 14 toseparate. Unlike a packing seal, the sealing ability of the seal 38 isnot affected by separation of the pipe sections 12, 14.

Referring now to FIGS. 1-4, a series of annular bearing races 46 areformed in the outer surface of the first end 18 of the first pipesection 12 and the inner surface of the sleeve 26. The bearing races 46hold a plurality of bearings 48. The bearings 48 are preferably ballbearings. The bearings 48 allow the pipe sections 12, 14 to rotate aboutone another so that the pipe sections 12, 14 may be oriented indifferent directions.

The bearings 48 may be incorporated into the joint 10 after the pipesections 12, 14 are joined together. To do this, a bearing opening 50 isformed in the center of each bearing race 46 in the sleeve 26. As shownin FIG. 4, the bearing openings 50 are radially spaced around the sleeve26. The bearings 48 may be inserted into the bearing races 46 throughthe bearing openings 50. Once each bearing race 46 is filled withbearings 48, a plug 52, shown in FIG. 1, may be inserted into eachbearing opening 50 to secure the bearings 48 within the joint 10. Thepipe sections 12, 14 remain connected to form the joint 10 after thebearings 48 are inserted, because the bearings 48 prevent relativelongitudinal movement between the pipe sections 12, 14.

Grease is used to lubricate the bearings 48. Grease may be incorporatedinto the joint 10 through the plug 52 using a grease zerk and grease gun(not shown). The grease zerk may thread into the plug 52 and feed greasefrom the grease gun into the joint 10. The grease is maintained withinthe joint 10 via a low pressure seal 54. The low pressure seal 54 mayonly seal fluid up to 100 psi or less. The low pressure seal 54 isannular and positioned around the outer circumference of the first end18 of the first pipe section 12 proximate the first end 36 of the sleeve26. The low pressure seal 54 also prevents outside contaminants fromentering the joint 10.

With reference to FIG. 1, a weep hole 56 is formed in the sleeve 26between the seal 38 and the bearings 48. The weep hole 56 is a narrowpassage that interconnects the inner and outer surface of the sleeve 26.If any fluid leaks around the seal 38 during operation, the fluid may bedrained from the joint 10 through the weep hole 56. The weep hole 56helps prevent any fluid within the joint 10 from reaching the bearings48.

Continuing with FIG. 1, the body section 20 has a wall thickness A. Thehigh pressure fluid passing through the joint Ito may erode at the firstwall thickness A over time. Due to this, the wall thickness isordinarily used in swivel joints 10 to judge the wear on the joint todetermine whether or not the joint 10 has entered a failure mode. If thewall thickness A of the joint 10 has decreased beyond a certainthreshold, the joint 10 may no longer be considered suitable for use.For example, the joint 10 may is no longer be considered suitable foruse if the wall thickness A has decreased by 50% or 70%, depending onthe characteristic of the body section 20.

With reference to FIGS. 1-2, the first surface 22 has a second wallthickness B, as shown in FIG. 2, that may be smaller than A. The wallthickness B also has a failure mode. The wall thickness B is consideredto have failed if the wall thickness has decreased so that the joint 10is no longer properly sealed. If a facial or packing seal placed betweenthe surfaces 22, 30 is used instead of the radial seal 38, the thicknessB may fail before the thickness A fails. This is because the packingseal will lose its sealing ability if the thickness of B is reduced. Incontrast, the sealing ability of the radial seal 38 is not affected by adecrease in thickness of B. Therefore, by using a radial seal 38, thethickness A will reach the failure mode before the thickness B.

The thickness B may also be increased throughout the embodimentsdiscussed herein. Increasing the thickness B extends the amount of timethe first surface 22 will seal properly before it fails. An example ofan increased wall thickness B is shown in FIG. 11.

Turning now to FIG. 5, a second radial seal 58 may also be used in thejoint 10. The second seal 58 may be positioned axially between the firstradial seal 38 and the weep hole 56. Alternatively, the second seal 38may be positioned between the weep hole 56 and the bearings 48. Thesecond seal 58 may serve as a back-up seal if fluid starts to leak pastthe first seal 38. The second seal 58 may have a circular profile. Forexample, the second seal 58 may be an O-ring. Alternatively, the secondseal 58 may have a rectangular profile. The second seal 58 may also be arotary seal. The second seal 58 may be made out of an elastic materialcapable of sealing fluid, such as nitrile, polyresin, silicone, orpolyurethane.

The second radial seal 58 may be inserted into a second annular groove60 that is identical to the first groove 40. However, the second groove60 may be smaller in size depending on the size of the second seal 58.The second seal 58 may also just fit around the outer circumference ofthe first end 18.

Turning now to FIGS. 6-8, an alternative embodiment of the high pressureswivel joint 100 is shown. The joint 100 does not contain the seal 38and groove 40. Instead, the joint 100 comprises a first radial seal 102that is positioned in a first annular groove 104. The remainingcomponents of the joint 100 are identical to those in joint 10, shown inFIG. 1.

The groove 104 is formed around the inner surface of the sleeve 26,rather than the outer surface of the first end 18, as shown in FIG. 1.The groove 104 is axially spaced from the internal surface 30 of thesleeve 26, and is characterized by a pair of parallel side walls 106joined by a base 108, as shown in FIG. 7.

Like the seal 38, the seal 102 is a rotary seal that allows for rotationof the first end 18 within the sleeve 26. For example, the seal 102 maybe a u-cup seal or have a rectangular profile. Alternatively, the seal102 may have a circular profile. The seal 102 may be made from anelastic material capable of sealing fluid.

The seal 102 contacts the side walls 106 and the base 108 of the groove104 when inserted into the groove 104. The seal 102 seals against theouter surface of the first end 18 of the first pipe section 12. The seal102 does not contact either of the surfaces 22, 30. The seal 102 onlycontacts the groove 104 and the outer circumference of the first end 18of the first pipe section 12.

Turning now to FIG. 9, a second radial seal 110 may also be used in thejoint 1000. The second seal 110 may be positioned axially between thefirst radial seal 102 and the weep hole 56, as shown in FIG. 9.Alternatively, the second seal 110 may be positioned between the weephole 56 and the bearings 48. The second seal 110 may serve as a back-upseal if fluid starts to leak past the first seal 102. The second seal110 may have a circular profile. For example, the second seal 110 may bean O-ring. Alternatively, the second seal 110 may have a rectangularprofile. The second seal 110 may also be a rotary seal. The second seal110 may be made out of an elastic material capable of sealing fluid,such as nitrile, polyresin, silicone, or polyurethane.

The second seal 110 may be inserted into a second annular groove 112that is identical to the first groove 104. However, the second groove112 may be smaller in size depending on the size of the second seal 110.The second seal 110 may also just fit around the outer circumference ofthe first end 18.

Turning back to FIG. 5, during operation, the first seal 38 will wearagainst the inner circumference of the sleeve 26. Over time, such wearmay affect the ability of the seal 38 to seal properly against thesleeve 26. In such case, the second pipe section 14 will need to bereplaced. However, the groove 40 in the first end 18 and the surroundingarea of the first end 18 should remain relatively intact. This isbecause wear from the seal 38 is transferred to the inner circumferenceof the sleeve 26. If a second seal 58 is used, the wear from the secondseal 58 will also be transferred to the sleeve 26.

Likewise, with reference to FIG. 9, the first seal 102 will wear againstthe outer circumference of the first end 18 of the first pipe section 12during operation. Over time, such wear may affect the ability of theseal 102 to seal properly against the first end 18. In such case, thefirst pipe section 12 will need to be replaced. However, the groove 104in sleeve 26 and the surrounding area of the sleeve 26 should remainrelatively intact. This is because wear from the seal 102 is transferredto the outer circumference of the first end 18 of the first pipe section12. If a second seal 110 is used, the wear from the second seal 110 willalso be transferred to the sleeve 26. An operator may choose whichembodiment of the joint 10 or 100 to use based on which pipe section 12,14 the operator prefers to replace over time.

Turning now to FIGS. 10-11, an alternative embodiment of the swiveljoint 200 is shown. The first end 18 of the first pipe section 12 has afirst annular groove 202 formed around its outer surface. The firstgroove 202 is axially spaced from the first surface 22 and ischaracterized by side walls 204 joined by a base 206. A first radialseal 208 is positioned within the first groove 202. At least a portionof the first seal 208 contacts both side walls 204 and the base 206 ofthe groove 202 when the first seal 208 is positioned within the firstgroove 202.

The sleeve 26 has a second annular groove 210 formed around its innersurface. The second groove 210 is axially spaced from the internalsurface 30 and is characterized by side walls 212 joined by a base 214.A second radial seal 216 is positioned within the second groove 210. Atleast a portion of the second seal 216 contacts both side walls 212 andthe base 214 of the groove 210 when the second seal 216 is positionedwithin the second groove 210. Like the seals 38 and 102, the first andsecond seals 208 and 216 may have a circular or a rectangular profileand be made out of an elastic material capable of sealing fluid, such asnitrile, polyresin, silicone, or polyurethane.

As shown in FIG. 10, the first groove 202 and the second groove 210 arecoaxial. An annular wear ring 218 is positioned between the grooves 202and 210. The wear ring 218 has a rectangular profile. The seals 208 and216 seal against opposite sides of the wear ring 218. The wear ring 218need only be wide enough axially to provide a contact surface for theseals 208, 216, but may be wider. The wear ring 218 is held in placebecause it is situated between an annular shoulder 220 formed on thefirst end 18 of the first pipe section 12 and the internal surface 30 ofthe sleeve 26. The wear ring 218 may be made of a hardened material,such as stainless steel.

During operation, the first seal 208 and the second seal 216 will wearagainst opposite sides of the wear ring 218. Any damage caused by theseals 208 and 216 rubbing against the wear ring 218 will be primarilyinflicted on the wear ring 218. The seals 208, 216 and grooves 202 and210 will remain relatively intact. Due to this, only the wear ring 218will need to be replaced over time, rather than one of the pipe sections12, 14. The wear ring 218 may also be formed out of a material that isresistant to corrosion to lengthen the life of the wear ring 218.

A rubber gasket 222 may also be bonded to the base of the wear ring 218,as shown in FIG. 11. The gasket 222 may act as a facial seal between thesurfaces 22, 30. The gasket 222 may help cushion and reduce frictionbetween the surfaces 22, 30 during operation.

To manufacture the swivel joints 10, 100, or 200, the pipe sections 12,14 are first machined from pieces of metal. The shape of the pipesections 12, 14 and the features, such as the bearing races 46 andbearing openings 50, are formed at the time the pipe sections 12, 14 aremachined. After the pipe sections 12, 14 are machined, the pipe sections12, 14 are typically heat treated. Heat treating the pipe sectionsincreases the hardness of the pipe sections 12, 14 and helps resistagainst corrosion. The pipe sections 12, 14 are typically heated up to1,800-1,900° F.

The problem with heat treating the pipe sections 12, 14 after they aremachined is that the pipe sections 12, 14 may become distorted duringthe heat treatment process. If the pipe sections 12, 14 are distortedduring heat treatment, it may be difficult to get the pipe sections 12,14 to seal properly. Additionally, if the bearing races 46 are distortedduring the heat treatment, the joints 10, 100, and 200 will not rotateproperly.

One way to prevent distortion of the pipe sections 12, 14 during theheat treatment: is to increase the wall thickness of the first end 18and the sleeve 26. The thicker the walls, the less likely the pieceswill distort during heat treatment. A grinding operation may also beused after the first end 18 and the sleeve 26 are heat treated to removeany distortion in the pieces. The thicker the walls of the first end 18and the sleeve 26, the more surface area available to grind the piecesto the appropriate specifications.

Another method for preventing distortion is to heat treat the metalbefore the joint 10, 100 or 200 is machined. This would avoid anyunwanted distortion caused to the machined areas by the heat treatment.The bearing races 46 may be machined over-sized after the pipe sections12, 14 are heat treated, and then coated to a desired depth with aspecial coating. The coating may be any thermal spray coating, HVOFcoating, or Nano-layered coating such as Modumetal. The coating is thenground to the desired specifications. The coating may serve as ahardened surface on the bearing races 46 for the bearings 48 to rotatewithin. The coating may also be used on the surfaces 22, 30 and groundto the desired specifications.

After the pipe sections 12, 14 are machined, the grooves 40, 104, 202 or210 may be formed in the first end 18 and/or the sleeve 26. Followingformation of the grooves 40, 104, 202 or 210, the seals 38, 102, 208 or216 may be inserted into the groove(s). Once the seals 38, 102, 208 or216 are in place, the first end 18 may be inserted in the sleeve 26. Thebearing races 46 are each filled with bearings 48 by inserting thebearings 48 through the bearing openings 50. The plugs 52 may then besecured within each bearing opening 50. Grease may be inserted into thejoint 10, 100, or 200 through the plugs 52. Once the joint 10, 100, or200 is filled with grease, the joint may be incorporated for use in apipe assembly.

Turning now to FIG. 12, an alternate embodiment of the swivel joint 300is shown. The joint 300 comprises a tubular first member or pipe section312 and a tubular second member or pipe section 314. Fluid flows betweenthe pipe sections 312, 314 through a passage 316.

The pipe sections 312 and 314 have substantially the same shape andconstruction as the pipe sections 12 and 14, shown in FIG. 5. However,unlike pipe sections 12 and 14, a first wear ring 318 and a second wearring 320 are positioned around the inner diameters of the pipe sections312 and 314.

Over time, wear may occur to an inner wall 322 of a connection end orfirst end 324 of the first pipe section 312. The wear may occurproximate a seal 326 positioned in an annular groove 328 formed in thefirst section 312 and axially spaced from a first surface 330 of thefirst section 312. The wear may cause the inner wall 322 of the firstend 324 to start to erode towards the groove 328. The inner wall 322 mayerode so much that the integrity of the groove 328 is compromised.

Wear may also occur over time to an inner wall 332 of a connection endor sleeve 334 of the second pipe section 314. The wear may occuradjacent a recessed internal surface or face 336 formed in the sleeve334. If wear occurs to the inner walls 322 and 332 of the pipe sections312, 314, the joint 300 may no longer seal properly.

To prevent excess wear or erosion to the inner wall 322 of the first end324, the first wear ring 318 may be positioned around tile inner wall322 of the first end 324. Likewise, to prevent excess wear or erosion tothe inner wall 332 of the sleeve 334, the second wear ring 320 may bepositioned around the inner wall 332 of the sleeve 334.

As fluid passes through the joint 300, the fluid may wear against thewear ring 318 or 320 instead of the inner walls 322 or 332 of the firstend 324 or sleeve 334. Thus, the erosion caused by the wear is impartedto the wear ring 318 or 320 and not the inner walls 322 or 332. If thewear ring 318 or 320 has suffered too much wear, it can be replaced witha new wear ring. This helps to extend the life of the first end 324 andthe sleeve 334.

The first wear ring 318 is positioned within a first annular recess 338formed in the inner wall 322 of the first pipe section 312 and extendingfrom its connection end 324. The recess 338 is bounded by a side wall340 joined to a base 342. The recess 338 surrounds the fluid passage 316and is concentric with it.

Likewise, the second wear ring 320 is positioned within a second annularrecess 344 formed in the inner wall 332 of the second pipe section 314and extends from is its internal face 336. The recess 344 is bounded bya side wall 346 joined to a base 348. The recess 344 surrounds the fluidpassage 316 and is concentric with it.

With reference to FIGS. 14-16, the first wear ring 318 is shown moredetail. The first wear ring 318 has a first surface 319 joined to asecond surface 321 by parallel side walls 323. The first wear ring 318has a rectangular cross-sectional shape. In alternative embodiments, thewear ring 318 has a circular cross-sectional shape. To lengthen itslife, the wear ring 318 is preferably formed from a hardened materialthat is resistant to corrosion, such as stainless steel. The second wearring 320 has the same shape and construction as the first wear ring 318.The wear rings 318 and 320 are formed as separate pieces from the pipesections 312 and 314.

Turning back to FIG. 12, the wear rings 318 and 320 are removable fromthe pipe sections 312 and 314. The first wear ring 318 fits tightlybetween the side wall 340 of the recess 338 and the first surface 319 ofthe second wear ring 320. The second wear ring 320 fits tightly betweenthe side wall 346 of the recess 344 and the second surface 321 of thefirst wear ring 318. These tight fits restrain the rings' 318, 320 axialmovement. Lateral movement of each of the wear rings 318 and 320 isrestrained by the base 342, 348 of the recess 338, 344 within which itis received. Each wear ring 318, 320 may be press fit or slip fit withinits associated recess 338, 344.

Each of the wear rings 318 and 320 may rotate with its corresponding endwhen the swivel joint 300 is in use. In another embodiment, a seal orbuffer not shown) may be placed between the wear rings 318 and 320 toserve as a cushion.

While two wear rings are included in the embodiment shown in FIG. 12,other embodiments of a swivel joint may include only a single wear ring.For example, a swivel joint may include only a first wear ring withinthe first pipe section. Such a wear ring is held in place by the recess338 and the internal surface 336 of the sleeve 334. Similarly, a swiveljoint may include only a second wear ring within the section pipesection. Such a wear ring is held in place by the recess 344 and thefirst surface 330 of the first end 324.

Turning now to FIG. 13, another embodiment of the swivel joint,designated by reference number 400, is shown. The joint 400 comprises atubular first member or pipe section 412 and a tubular second member orpipe section 414. Fluid flows between the pipe sections 412, 414 througha passage 416.

The pipe sections 412 and 414 have substantially the same shape andconstruction as the pipe sections 12 and 14, shown in FIG. 10. However,unlike pipe sections 12 and 14, a first wear ring 418 and a second wearring 420 are positioned around the inner diameters of the pipe sections412 and 414. The wear rings 418 and 420 have the same shape andconstruction as the wear rings 318 and 320, shown in FIG. 12. The wearrings 418 and 420 are installed within the first and second pipesections 412 and 414 in the same manner that the wear rings 318 and 320are installed within the pipe sections 312 and 314.

Except as otherwise noted herein, the swivel joints 300 or 400 aremanufactured in the same way as the swivel joints 10, 100, or 200. Thewear rings 318 and 320 may be incorporated into any of the embodimentsof swivel joints described herein or into any other swivel joint formedfrom first and second pipe sections.

Changes may be made in the construction, operation and arrangement ofthe various parts, elements, steps and procedures described hereinwithout departing from the spirit and scope of the invention asdescribed in the following claims.

The invention claimed is:
 1. A swivel joint, comprising: a tubular firstconnector having a hollow end within which an internal face is formedand a first longitudinal axis; a tubular second connector having an endupon which an external face is formed and a second longitudinal axis,the end of the second connector received within the end of the firstconnector such that the first and second axes coincide, such that theconnectors are relatively rotatable about the coincident axes, and suchthat the faces engage at an interface extending within a plane normal tothe axes; an internal bore extending through each of the joined firstand second connectors; a first annular recess formed within the internalbore and at a position upstream from the interface; a first zone ofhardened wear material situated within the first recess; and in whichthe hardened wear material is press-fit within the first recess suchthat at least a portion of the hardened wear material directly engages awall or walls defining the first recess.
 2. The swivel joint of claim 1,further comprising: a second annular recess formed within the internalbore and at a position downstream from the interface; and a second zoneof hardened wear material situated within the second recess; in whichthe hardened wear material is press-fit within the second recess suchthat at least a portion of the hardened wear material directly engages awall or walls defining the second recess.
 3. The swivel joint of claim2, in which the second zone of hardened wear material is made ofstainless steel.
 4. The swivel joint of claim 2, in which the secondzone of hardened wear material comprises a second wear ring.
 5. Theswivel joint of claim 1, further comprising: a first seal interposedbetween the second connector and the first zone of hardened wearmaterial.
 6. The swivel joint of claim 1, in which the first zone ofhardened wear material is made of stainless steel.
 7. The swivel jointof claim 1, in which the first recess has a rectangular cross-sectionalshape.
 8. The swivel joint of claim 1, in which the first zone ofhardened wear material comprises a first wear ring.
 9. The swivel jointof claim 1, further comprising: a seal positioned within an annulargroove that is formed in an inner surface of the first connector, inwhich the annular groove is situated in a spaced relationship to theinterface.
 10. The swivel joint of claim 1, further comprising: a sealpositioned within an annular groove that is formed in an outer surfaceof the second connector, in which the annular groove is situated in anaxially spaced relationship to the interface.
 11. The swivel joint ofclaim 1, in which a seal does not contact the internal face of the firstconnector and does not contact the external face of the secondconnector.
 12. The swivel joint of claim 1, further comprising: a secondannular recess formed within the internal bore and at a positionupstream from the interface; and a second zone of hardened wear materialsituated within the second recess; in which the hardened wear materialis press-fit within the second recess such that at least a portion ofthe hardened wear material directly engages a wall or walls defining thesecond recess.
 13. The swivel joint of claim 12, in which the first andsecond zones of hardened wear material form a boundary of the internalbore.
 14. The swivel joint of claim 12, in which the first and secondzones of hardened wear material are formed as separate pieces.
 15. Theswivel joint of claim 12, in which the first and second zones ofhardened wear material are in communication with the internal bore. 16.A system, comprising: the swivel joint of claim 1; and a fluid having apressure of at least 5,000 pounds per square inch within at least aportion of the swivel joint.
 17. A swivel joint, comprising: a tubularfirst connector having a hollow end within which an internal face isformed and a first longitudinal axis; a tubular second connector havingan end upon which an external face is formed and a second longitudinalaxis, the end of the second connector received within the end of thefirst connector such that the first and second axes coincide, such thatthe connectors are relatively rotatable about the coincident axes, andsuch that the faces engage at an interface extending within a planenormal to the axes; an internal bore extending through each of thejoined first and second connectors; a first annular recess formed withinthe internal bore and at a position downstream from the interface; afirst zone of hardened wear material situated within the first recess;and in which the hardened wear material is press-fit within the firstrecess such that at least a portion of the hardened wear materialdirectly engages a wall or walls defining the first recess.
 18. Theswivel joint of claim 17, in which the internal face of the firstconnector contacts the external face of the second connector.
 19. Theswivel joint of claim 17, in which no objects are interposed between theinternal face of the first connector and the external face of the secondconnector at the interface.